Engine starter drive



Dec. 28, 1943. n. P. KEARNEY ENGINE STARTER DRIVE Filed July 15. 1942 I INVENTOR. Mimi 'oflalu'e Patented Dec. 28, 1943 U NITED ESTATES PATENT FEEQE T 2,337,559 :ENGINE'STARTERaDRIVE Daniel P. Kearney"; Birmingham,TMich.,- assignor to Bendix Aviation Corporation, South Bend, 11111., a corporation of Delaware Application July 15, 1942, Serial No. 450,963

3 Claims.

The present invention relates to an engine starter drive and more particularly to that type of drive which maintains the gear connection between the starting motor and engine until the engine is reliably self-operative.

It is an object of the present invention to provide a novel starter drive of this type which is reliable and efficient in operation and simple and economical in construction.

It is another object to provide such a device which is particularly well adapted for heavy duty installations.

It is another object to provide such a device which includes an overrunning clutch connection to the pinion.

It is a further object to provide such a device incorporating a unitary means for preventing the pinion from drifting away from its idle position and for holding the clutch in initial engagement.

Further objects and advantages will be apparent from the following description taken in connection with the accompanying drawing in which:

Fig. l is a side elevation partly broken away and in section of a preferred embodiment of the invention.

Fig. 2 is a detail in side elevation and partly in section of the drive pinion and associated parts in cranking position, and

Fig. 3 is a view similar to Fig. 2 showing the parts in the positions assumed durin overrunning of the pinion while held in cranking position.

In Fig. l of the drawing there is illustrated a power shaft I and a screw shaft 2 yieldably connected to rotate therewith by means of a drive spring 3 anchored to the power shaft at 4 and to the screw shaft at 5.

A nut 6 is threaded on the screw shaft 2, and a pinion I is journalled on the nut in position to be carried thereby into and out of engagement with a gear 8 of an engine to be started. An abutment 9 on the screw shaft is adapted to be engaged by the end of the pinion 1 when in cranking position, and a flange II is formed on the nut for engaging the opposite end of the pinion and clamping it to the abutment by the screw jack action of the screw shaft and nut. Clutch teeth l2 and I3 are preferably provided on the pinion I and flange H' to form a positive driving connection therebetween during the cranking operation.

According to the present invention centrifugal means are provided for preventing the nut 6 from returning to idle position while the screw shaft is rotating above a predetermined speed,

the screw shaft and normally maintained by a spring H3 in a retracted position as shown in Fig. 2 where it does not interfere with the travel of the nut on the screw shaft. Rotation of the screw shaft above a predetermined speed during 10 the cranking operation causes the latch to move out by centrifugal force to the position shown in Fig. 3 where it limits the return movement of the nut to an amount sufficient to release the pinion from its clutching engagement.

A spring [6 on the screw shaft is arranged to bear at one end against the abutment member 9 and at its other end against a thrust ring l'l within the bore of the pinion 1 whereby said spring holds the clutch teeth l2, [3 in initial engagement, and prevents the pinion from drifting away from idle position.

In operation, starting with the parts in the positions illustrated in Fig. 1, rotation of the power shaft l by the starting motor not illustrated is transmitted through the spring 3 to the screw shaft 2, whereby the nut 6 and its associated parts are caused to traverse to the right until the pinion 1 meshes with the engine gear 8 and engages the abutment 9. The pinion is then clutched positively to the screw shaft by the nut and is caused to rotate therewith to crank the engine.

When the engine starts, the acceleration of the engine gear 8 causes the pinion 'i to overrun the drive, thus threading the nut 6 back along the screw shaft until it engages the latch M as shown in Fig. 3. The clutch I2, 13 is thus opened permitting the pinion to overrun freely. If the engine should then fail to continue self-operative, cranking will be resumed as soon as the starting motor accelerates to a speed corresponding to the engine rotation. When the engine is reliably self-operative, deenergization of the starting motor by the operator permits the screw shaft to decelerate until the spring 15 withdraws the latch l4 whereupon the parts are returned to idle position.

Although but one embodiment of the invention 5 has been shown and described in detail, it will be understood that other embodiments are possible and that various changes may be made in the design and arrangement of the parts without departing from the spirit of the invention as defined in the claims appended hereto.

said nut and pinion being formed as clutch 10 means which are closed by the longitudinal pressure of the nut on the pinion when the pinion engages said stop, and means preventing the nut from returning to idle position while the screw shaft is rotating above a predetermined speed. 15

2. In an engine starter drive a shaft, a nut having a radial flange formed with clutch teeth threaded on the shaft, a pinion slidably journalled on the nut having teeth adapted to cooperate with said clutch teeth, an abutment on the shaft defining the operative position of the pinion, and a centrifugal latch preventing return of the nut to idle position while the shaft rotates above a predetermined speed.

3. A starter drive as set forth in claim 2 in cluding, further, spring means normally maintaining the pinion in idle position and holding the clutch teeth on the nut and pinion in engagement.

DANIEL P. KEARNEY. 

